Zika: Expert Advice for Travelers of All Ages

CDC Map of "Countries and Territories in the Americas with Active Zika Virus Transmission." Ed Note: in some cases an entire country is marked as "active" even though zika has only been reported in a small number of regions within that country. (Last updated 3/9/17)

CDC Map of "Countries and Territories in the Americas with Active Zika Virus Transmission." Ed Note: in some cases an entire country is marked as "active" even though zika has only been reported in a small number of regions within that country. (Last updated 3/9/17)

The World Health Organization (WHO) has declared Zika—a mosquito-borne virus spreading across the Americas—to be an international public health emergency. Researchers suspect that the virus is linked to Latin America’s marked increase in reports of microcephaly, in which a newborn has an unusually small head and, often, brain damage; and Guillain-Barré syndrome, an autoimmune disorder that can lead to muscle weakness and paralysis.

First discovered in 1947 in the Zika forest of Uganda, Zika was considered to be a common, non-fatal virus with mild symptoms. In fact, most people who have been infected never even know they’ve had it. But pregnant women and immune-compromised individuals may now be at risk. Many of us routinely travel to the Zika-affected areas (see CDC list of affected areas) for work and leisure, and we naturally have concerns about safety for ourselves and for our families.

Zika Quick Guide*

• Zika is transmitted through the bite of an infected Aedes mosquito. There are reports of transmission through sexual activity and blood transfusions.
• Only 20% of infected people will experience symptoms. Most will recover and never know they had it.
Symptoms may include fever, rash, joint pain, and red eyes (conjunctivitis). In Dr. Callahan’s experience 10 to 15% of patients have a sore throat and/or severe fatigue. 

• Symptoms typically begin 2 to 7 days after being bitten. There is no vaccine or medicine for Zika.
• Zika clears from your system in 14 days. There is no evidence to suggest that it can harm your future unborn children if you are not pregnant at the time you get Zika.
• Dr. Callahan's favorite chemical mosquito repellants: permethrin, picaridin, and DEET at 30%.
Children traveling to the tropical Americas need to be up-to-date on vaccinations, so that if they get sick there’s no confusion about whether they are suffering from a vaccine-preventable disease or from Zika, chikungunya, or dengue.
Women who are pregnant or trying to get pregnant are advised against travel to affected areas. To date, there are no reports of women passing Zika to their children through breastfeeding.
Adults of child-bearing age are advised to use barrier contraceptives during travel to the tropical Americas and for a period of time upon return.
Patients who are immune compromised or who are on antibody therapy need to seek physician advice before they travel to the Tropical Americas.

Dr. Michael Callahan, a clinical associate physician in the Division of Infectious Diseases at Massachusetts General Hospital/Harvard Medical School, has a boots-on-the-ground perspective on Zika. Dr. Callahan is an expert in tropical medicine, mass casualty care, and rescue medicine. From 2005-2012 he led DARPA's biodefense program, focused on predicting emerging virus threats and developing treatments before they hit. Below are edited excerpts from the interview.

Leslie Michelson: Michael, what’s the background on this disease?
Dr. Michael Callahan: Zika is transmitted from the bite of an infected mosquito, and it’s found in two types of mosquitoes in the Aedes family. [Ed. Note: The two mosquitoes are Aedes aegypti, which originated in Africa; and Aedes albopictus, originally from Asia. Both mosquitoes are found worldwide in tropical and subtropical regions]. The Aedes mosquito has been around for a while. In Asia and Africa it’s the vector, the transmitting agent, for about 11 diseases, the most common of which are dengue fever, chikungunya, and now Zika. For reasons related to global migration, Zika has migrated from Africa and Asia, where’s it’s widespread and not particularly alarming. In about 2010, Zika was found on the Micronesian islands, the Caroline Islands, Guam, Yap, and there have been a couple cases in Hawaii. More recently, it made a big jump into the Amazonia, particularly Brazil.

Why has Zika taken hold in the tropical Americas?
The people of Brazil, South America, Central America and elsewhere have never been affected by Zika before—meaning, they are an immunologically naïve population. So everybody is sensitive and more people get symptomatic with Zika. In Africa and Asia, lots of people have had Zika and developed immunity, so they don’t appear to get re-infected and don’t get new Zika. This is the first time Brazil has seen Zika and it has spread like wildfire. 

If a woman is pregnant or trying to get pregnant, what does she need to know?
In an abundance of caution, for the next month, while we clarify the association between Zika and microcephaly, we recommend against pregnant women traveling to the tropical Americas, particularly in the first and second trimester. This is a part of the world that has three rapidly escalating infectious diseases taking off: dengue fever has been here, but it’s increasing dramatically; chikungunya has not been to the Americas before and it’s increasing dramatically; and Zika is brand new to the Americas and it’s increasing dramatically. Unless absolutely required, defer travel to these areas.

Dr. Michael Callahan

Dr. Michael Callahan

Are you and your team studying the link between Zika and microcephaly?
We’re deeply into it. The CDC [Centers for Disease Control and Prevention], WHO, and PAHO [Pan American Health Organization] are deeply into it. We’re tracking patients in Columbia, Panama, and Brazil, and infected travelers returning to the United States, and through our international network.

We think it’s probably not just the virus by itself. In other words, is there a patient factor? Something in Brazil? Something in the environment?

Tens of millions of people in Asia and Africa have been infected with Zika and they have not seen a microcephaly link. Yet there’s a massive increase in microcephaly cases in Brazil. We accept that they are real, but we’re trying to unwind whether or not they’re due to 1. Zika alone; 2. Zika + being Brazilian; or 3. Zika + being infected while you’re in Brazil. Restated: Is it the virus? We think it’s probably not just the virus by itself. In other words, is there a patient factor? Something in Brazil? Something in the environment? And that’s what we need to solve—to show a legitimate connection between microcephaly cases and Zika. We think the story will be clarified in the coming months. But for right now, we cannot pin it purely on Zika.

But, in general, if you’re pregnant or may become pregnant, your recommendation is: Don’t go.
Exactly. Point #1 is: Why travel now? Let’s revisit this in a month. Because the all the great institutions of Central and South America are pursuing this with vigor and will figure out whether or not Zika is associated with microcephaly.

Point #2 is: All people traveling to this area have a very small risk of contracting Guillain-Barré syndrome, which can be a devastating disease, in which your immune system basically gets confused after fighting the virus. The same antibodies that helped you get over Zika become misdirected and attack your own body, causing damage to the nerve tissue, weakness, fine-motor incoordination and, most ominously, failure of respiratory muscles. It’s your immune system overreacting. If we include all patients who get Zika—both symptomatic and asymptomatic—the actual number who get Guillain-Barré is now between 1 in 10,000. Guillain-Barré is not necessarily unique to Zika, but it happens. So it should be considered. 

Point #3 is: If you choose to go—which I understand people must, for reasons of work or leisure—use mosquito-deterrents and protective measures.

What’s the best way to avoid mosquito bites?
Chemical protectants. Here are three proven repellants—all of which are considered safe during pregnancy—in my order of favorites: #1 on my list is permethrin—spray it on the clothing, not the person; #2 is picaridin, a newer generation mosquito deterrent; #3 is DEET (diethyltoluamide), and get one that’s around 30% DEET, because 20% does show defects, but 40% doesn’t help you anymore—so 30% is ideal. At this time, there is little evidence to support the effectiveness of newer “all natural” repellants that do not include the above ingredients. 

Secondary measures include wearing light clothing, and long-sleeve pants and shirts. Mosquitoes don’t like white clothing because they know they stand out. I always bring light-colored clothing when I’m traveling to mosquito-endemic areas. And avoid floral prints. Mosquitoes actually feed on nectar and are attracted to flowers. So just like you wouldn’t wear a floral print shirt outside if you are allergic to bees, you shouldn’t do it for mosquitoes either.

Dengue, chikungunya, and Zika aren’t pleasant. But they are inherently survivable for children and the elderly.

Also, you want to avoid mosquito habitats. Malarial mosquitoes love the wilderness. But the Aedes mosquito breeds in urban centers, loves indoor habitats, and loves people. It can breed in a bottle-cap of water, so, rain gutters, old tires, a soda pop can with a little bit of water in it are havens for this mosquito to breed in. Make sure you’re not near standing-water sources or trash dumps.

And always stay in hotels with screened-in rooms with ceiling fans and/or air conditioning. But please do not be comforted by the splendor of a luxury resort. They provide you no protection from a mosquito that flies two miles from the local slum or barrio and lands in the nice four- and five-star hotel. It’s an equal opportunity disease. And while it’s found more in urban slums, it’s significantly distributed regardless of socioeconomic class or infrastructure… So, just a warning about nice hotels: They can’t protect you.

They may guarantee you clean water, but they can’t guarantee you a mosquito-free environment.
Clean water, good food, make sure you don’t get a bad raw oyster, typically. But, yes, you still need to practice protective measures.

To summarize: Chemical protectants; screened-in, ceiling-fan or air-conditioned hotels; light clothing, and no floral prints?
Right. And another tip: Get the bungalow closer to the on-shore breeze. Because mosquitoes are attracted to you by three things: 1. Your carbon dioxide, 2. Your heat, 3. A visual lock. The mosquito finds you because you’re breathing and your CO2 goes downwind. A mosquito 300 yards away flies across that plume of CO2, and thinks, ‘Hey there’s an animal up there.’ It takes them tens of minutes to cover the distance. Once they get closer, they get a heat signature, then they move in. At 30 feet, they hone in and go to visual, then they figure out where they’re going to land. They hover around you searching for a while, looking for the right spot, before they come in to bite. Pretty diabolical.

What special precautions do we need to take for our children?
Children are not advised against traveling to the tropical Americas, but make sure before they go that they’re updated on all their vaccines. To be clear: There are no vaccines for dengue fever, chikungunya, or Zika, and your children’s routine vaccination won’t protect them, but it will help to avoid creating any confusion should they get ill. Because if they do get sick, it’s extremely helpful for your physicians to know that they don’t have the vaccine-preventable big-problem diseases like pertussis and measles, which are disastrous in children and adults. So get those off the list, just vaccinate before you go. That shuts 9 out of 10 doors for us, so we can get to the other diseases—which are no holiday. Dengue, chikungunya, and Zika aren’t pleasant. But they are inherently survivable for children and the elderly.

I would turn up the prudishness for any adolescent traveling on spring break to the tropics. This disease is more likely to have a profound impact on the early weeks of pregnancy.

What about travelers who have autoimmune diseases or are on immune-compromising therapies?
There’s less data available on patients who have had organ transplants, suffer from diabetes, rheumatoid arthritis, or have HIV, etc…. And that brings up another point. A unique risk for the global affluent is that they live in therapy-rich environments and/or they have access to the newest therapeutics. They tend to be the first to get new, expensive FDA-approved treatments. So when they go on holiday or on business in the tropics, it’s a Darwinian challenge test. If they have an autoimmune disease and are being treated with the latest immune-altering drugs, there are very few people in that situation who have met the true wilderness and these exotic diseases before. Think about it: How many people in Laos who are exposed to these infectious diseases have been put on rituximab? 

For patients who have access to quality medical care, which includes novel, unprecedented, powerful drugs for rheumatoid arthritis, Crohn’s disease, IBD, lupus, and others, one needs to take a breath, slow down, and more carefully consider their unique risks should they encounter a tropical disease that has never seen their type of therapy before. Unhappily, even the most sophisticated travel medicine screening experts are unaware or inexperienced in the expanded risk posed by these unique travelers and the exotic diseases they might encounter in the tropics. And we don’t know what’s going to happen to these patients. I can’t tell you that they’d be any worse. We have no data. But people who have intentional immune suppression, predominantly from antibody therapy, need to seek physician advice before they travel to Zika-chikungunya-dengue-endemic areas. 

Michael, in the next month, college kids will be heading to places across Central America for spring break. If you’re the parent of a 19-year-old with a plane ticket, what do you tell them?
I would tell all men and all women of childbearing age to practice absolute barrier contraception. I would turn up the prudishness for any adolescent—and their adult chaperones—traveling on spring break to the tropics. They may insist that they are abstinent, but they may choose to not abstain during their period abroad. On two occasions, Zika has been proven to be sexually transmitted, and this disease is more likely to have a more profound impact on the early weeks of pregnancy. 

For women who are not pregnant, but want to be some day, do they need to be concerned about Zika now? Will it affect their future prospects?
The female who is not pregnant is fine. Your immune system gets fired up and pretty much stomps these viruses out. And while we believe there is residual Zika in semen after a man’s symptoms go away—it’s perceived to last for days, and not for weeks. More work, however, needs to be done to characterize this risk. Having said that, if your boyfriend has a febrile illness (a fever of uncertain cause), whether or not he’s been diagnosed with Zika, it’s a good time to wear a condom until Zika can be ruled out by his primary care physician or an infectious-disease consultant. For example: If a couple goes to Brazil, she’s fine, no problems, but he comes back and two days later, gets febrile and toughs it out—that guy uses barrier contraception until he is a) vindicated by a blood test to prove that he doesn’t have Zika, or b) the couple comes to a mutual agreement that he is convalescent and whatever he had is gone. And that’s a personal decision.

How long after you’ve had Zika is it safe to become pregnant?
There’s no definitive evidence as to the time required to ensure safety. There’s perceived to be no problem after a period—weeks to months—of convalescence. But we don’t know for sure how long. We’ve just never seen problems before with women in Africa and Asia having an increased risk in malformations. So we don’t have the data at this time. But people with Zika don’t keep Zika. It’s a fragile virus and a normal immune system is quite robust and can mount an effective immune response, and then the virus goes away. The period of viremia—that’s when a virus can be detected circulating—is typically no more than 14 days using our most sensitive blood assays. And it’s closer to 5 to 10 days for the majority of the population who have been confirmed with Zika. But a huge percentage of the population never knew they had Zika. They’re febrile one morning, then they’re fine. Their body got on it, and the virus disappeared. So the point is: There should be a period of care about getting an intentional or unintentional pregnancy after you or your partner returns from the tropical Americas.